From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 62E13C433EF for ; Tue, 8 Mar 2022 06:34:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6B80A8D0002; Tue, 8 Mar 2022 01:34:23 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 666998D0001; Tue, 8 Mar 2022 01:34:23 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 57CD88D0002; Tue, 8 Mar 2022 01:34:23 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0097.hostedemail.com [216.40.44.97]) by kanga.kvack.org (Postfix) with ESMTP id 4486D8D0001 for ; Tue, 8 Mar 2022 01:34:23 -0500 (EST) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id F22BDAA07D for ; Tue, 8 Mar 2022 06:34:22 +0000 (UTC) X-FDA: 79220254806.26.2A128BF Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf16.hostedemail.com (Postfix) with ESMTP id 3C6C0180005 for ; Tue, 8 Mar 2022 06:34:22 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KCQQz1CQ7z1GCHB; Tue, 8 Mar 2022 14:29:31 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Tue, 8 Mar 2022 14:34:17 +0800 Subject: Re: [PATCH 13/16] mm/migration: return errno when isolate_huge_page failed To: Baolin Wang , CC: , , , , , , , , , , , , , , , , , References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-14-linmiaohe@huawei.com> <3d286f44-e91d-b68d-63f2-e66529e3fa54@linux.alibaba.com> From: Miaohe Lin Message-ID: <257f4e4b-aaab-824c-9a68-6dc88d7f988f@huawei.com> Date: Tue, 8 Mar 2022 14:34:17 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <3d286f44-e91d-b68d-63f2-e66529e3fa54@linux.alibaba.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 3C6C0180005 X-Stat-Signature: x5wij47pw163mt7phmt4ytqxrz3c1g9x Authentication-Results: imf16.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf16.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-HE-Tag: 1646721262-776081 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/3/8 9:32, Baolin Wang wrote: >=20 >=20 > On 3/7/2022 8:20 PM, Miaohe Lin wrote: >> On 2022/3/7 10:14, Baolin Wang wrote: >>> Hi Miaohe, >>> >>> On 3/4/2022 5:34 PM, Miaohe Lin wrote: >>>> We should return errno (-EBUSY here) when failed to isolate the huge= page >>>> rather than always return 1 which could confuse the user. >>>> >>>> Signed-off-by: Miaohe Lin >>>> --- >>>> =C2=A0=C2=A0 mm/migrate.c | 6 ++---- >>>> =C2=A0=C2=A0 1 file changed, 2 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/mm/migrate.c b/mm/migrate.c >>>> index 6c2dfed2ddb8..279940c0c064 100644 >>>> --- a/mm/migrate.c >>>> +++ b/mm/migrate.c >>>> @@ -1618,10 +1618,8 @@ static int add_page_for_migration(struct mm_s= truct *mm, unsigned long addr, >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 goto ou= t_putpage; >>>> =C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (PageHuge(page)) { >>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (PageHead(page)) { >>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 = isolate_huge_page(page, pagelist); >>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 = err =3D 1; >>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } >>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (PageHead(page)) >>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 = err =3D isolate_huge_page(page, pagelist) ? 1 : -EBUSY; >>> >>> Could you elaborate on which case the huge page isolation can be fail= ed in this case? Or you met a real problem? Cause now we've got this head= huge page refcnt, I can not see why we'll fail to isolate this huge page= . >> >> IIUC, this could happen when hugepage is under migration which cleared= HPageMigratable. Page refcnt cannot >> prevent isolate_huge_page from happening. Or am I miss something? >=20 > Yes, that's possible. Thanks for your explanation. It will be better if= you can copy the possible scenario description to the commit log to help= other understand the issue. >=20 Sounds reasonable. Will do. Many thanks for review. > Reviewed-by: Baolin Wang > .